Electrical connectors provide signal connections between electronic devices using electrically-conductive contacts, or electrical contacts. In some applications, an electrical connector provides a connectable interface between one or more substrates, e.g., printed circuit boards. Such an electrical connector may include a receptacle connector mounted to a first substrate and a complementary header connector mounted to a second substrate. Typically, a first plurality of electrical receptacle contacts in the receptacle connector is adapted to mate with a corresponding plurality of electrical header contacts in the header connector. For instance, the electrical receptacle contacts can receive the electrical header contacts so as to establish an electrical connection between the electrical receptacle contacts and the electrical header contacts.
The electrical contacts typically include a plurality of signal contacts and ground contacts. Often, the signal contacts are so closely spaced that undesirable interference, or “cross talk,” occurs between adjacent signal contacts. As used herein, the term “adjacent” refers to contacts (or rows or columns) that are next to one another. Cross talk occurs when one signal contact induces electrical interference in an adjacent signal contact due to intermingling electrical fields, thereby compromising signal integrity. With electronic device miniaturization and high speed, high signal integrity electronic communications becoming more prevalent, the reduction of cross talk becomes a significant factor in connector design.
One commonly used technique for reducing cross talk is to position separate electrical shields, in the form of metallic plates, for example, between adjacent signal contacts. The shields act to block cross talk between the signal contacts by blocking the intermingling of the contacts' electric fields. The ground contacts are also frequently used to block cross talk between adjacent differential signal pairs.
Because of the demand for smaller, lower weight communications equipment, it is desirable that connectors be made smaller and lower in weight, while providing the same performance characteristics. Shields take up valuable space within the connector that could otherwise be used to provide additional signal contacts, and thus limit contact density (and, therefore, connector size). Additionally, manufacturing and inserting such shields substantially increase the overall costs associated with manufacturing such connectors. In some applications, shields are known to make up 40% or more of the cost of the connector. Another known disadvantage of shields is that they lower impedance. Thus, to make the impedance high enough in a high contact density connector, the contacts would need to be so small that they would not be robust enough for many applications.
It is desirable to provide an electrical connector that occupies a minimum amount of substrate space while reducing the occurrence of cross talk between the signal contacts of the electrical connector.